Thin film waveguide electrooptic modulator

ABSTRACT

This invention provides a thin film waveguide electrooptic intensity modulation device. The thin film waveguide is an isotropic organic medium which exhibits nonlinear optical response. The device is adapted to modulate waveguided radiation by refractive index change commensurate with change in an applied electric field.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 019,369 of the sametitle filed Feb. 26,1987, now U.S. Pat. No. 4,767,169.

BACKGROUND OF THE INVENTION

Electrooptic intensity modulators utilizing bulk inorganic crystals arewell known and widely utilized. Waveguide electrooptic modulators are amore recent development, and are described in literature such as AppliedPhysics Letters, 21, No. 7, 325 (1972); 22, No. 10, 540 (1973); and U.S.Pat. Nos. 3,586,872; 3,619,795; 3,624,406; 3,806,223; 3,810,688;3,874,782; 3,923,374; 3,947,087; 3,990,775; and references citedtherein.

One of the principal advantages of an optical waveguide configuration ascontrasted to bulk crystals is that much higher intensity electricfields may be used with the optical waveguide configuration and alsomuch lower capacitive values may be realized. Both of these operativecharacteristics are necessary to achieve high speed operation of suchelectrooptic modulators.

A thin film waveguide electrooptic modulator can operate employing oneof three modulating mechanism, i.e., Mach-Zehnder interferometry,directional coupling, or rotation of the optical polarization.

For a Mach-Zehnder interferometry type of electrooptical modulator, anoptical beam is guided into a linear thin film waveguide and split intotwo arms, one of which is sandwiched between a pair of electrodes, andsubsequently the arms are recombined into a single output beam. A phaseshift between the light guided in the two different arms occurs when avoltage is applied to the electrodes and creates a change in the indexof refraction in one of the arms due to either the Pockels or Kerreffect. The modulation of the output occurs since the beams in the twoarms either add or cancel when they recombine depending on the phaserelationship between them. The device requires a single mode linearwaveguide for beam splitting and recombination.

For the directional coupling type of modulator, the optical beam iscoupled into one of two adjacent linear waveguides and coupled out fromthe other guide. The amount of optical power which is transferred fromone guide to the other guide depends on the index of refraction of themedium between the channels. By applying an electric field and alteringthe index of refraction between the channels, the power transferred, andhence output from either guide, can be modulated.

The modulating mechanism for the polarization type of modulator is thephase shift between the transverse electric (TE) and transverse magnetic(TM) modes in the same waveguide due to an electric field appliedparallel or perpendicular to the surface of the waveguide which createsa directional change in the index of refraction in the waveguide due toa Pockels or Kerr nonlinear optical effect.

For a low voltage operating electrooptic modulator, highly responsivenonlinear optical media are required. LiNbo₃ has been an importantinorganic species for waveguide electrooptic modulator construction.However, there are certain inherent disadvantages in the use of LiNbO₃or other inorganic compound in an electrooptic modulator, such as thelimitation of the input optical power due to the inherentphotorefractive effect, and the high fabrication cost for a LiNbO₃ highquality crystal.

It is known that organic and polymeric materials with large delocalizedπ-electron systems can exhibit nonlinear optical response, which in manycases is a much larger response than by inorganic substrates.

In addition, the properties of organic and polymeric materials can bevaried to optimize other desirable properties, such as mechanical andthermoxidative stability and high laser damage threshold, withpreservation of the electronic interactions responsible for nonlinearoptical effects.

Of particular importance for conjugated organic systems is the fact thatthe origin of the nonlinear effects is the polarization of theπ-electron cloud as opposed to displacement or rearrangement of nuclearcoordinates found in inorganic materials.

Nonlinear optical properties of organic and polymeric materials was thesubject of a symposium sponsored by the ACS division of PolymerChemistry at the 18th meeting of the American Chemical Society,September 1982. Papers presented at the meeting are published in ACSSymposium Series 233, American Chemical Society, Washington D.C. 1983.

Organic nonlinear optical medium in the form of transparent thinsubstrates are described in U.S. Pat. Nos. 4,536,450; 4,605,869;4,607,095; 4,615,962; 4,624,872; and references cited therein.

The above recited publications are incorporated herein by reference.

There is continuing research effort to develop new nonlinear opticalorganic media and electrooptic devices adapted for laser modulation,information control in optical circuitry, and the like. The potentialutility of organic materials with large second order and third ordernonlinearities for very high frequency application contrasts with thebandwidth limitations of conventional inorganic electrooptic materials.

Accordingly, it is an object of this invention to provide a novelelectrooptic modulator.

It is another object of this invention to provide an electroopticintensity modulator which contains an organic nonlinear opticalcomponent.

It is a further object of this invention to provide a polymeric thinfilm waveguide electrooptic intensity modulator.

Other objects and advantages of the present invention shall becomeapparent from the accompanying description and figures.

DESCRIPTION OF THE INVENTION

One or more objects of the present invention are accomplished by theprovision of a thin film waveguide electrooptic intensity modulationdevice comprising (1) a transparent optical waveguiding thin film on asupporting substrate, wherein the thin film comprises an organic mediumwhich exhibits nonlinear optical response; (2) a pair of opticalinput-output coupling means which are structurally integrated with thewaveguiding thin film for coupling linearly polarized coherentelectromagnetic radiation to the said thin film, wherein the couplingmeans are in spaced positions such that an optical phase shift betweentransverse electric mode and transverse magnetic mode of waveguidedelectromagnetic radiation is an integral multiple of 2π and the outputradiation is linearly polarized; and (3) a pair of elongated stripelectrodes parallel to the waveguiding direction and situated in anintermediate zone between the positioned coupling means, and saidelectrodes are in a spaced proximity for application of a uniformelectric field to the thin film waveguide.

In another embodiment this invention provides a thin film waveguideelectrooptic intensity modulation device comprising (1) a transparentoptical waveguiding thin film on a supporting substrate, wherein thethin film comprises an isotropic organic polymer medium which exhibitsnonlinear optical response, and the waveguiding thin film is laminatedbetween two cladding layers which have a lower index of refraction thanthe cladded thin film; (2) a pair of optical input-output coupling meanswhich are structurally integrated with the waveguiding thin film forcoupling linearly polarized coherent electromagnetic radiation to thesaid thin film, wherein the coupling means are in spaced positions suchthat an optical phase shift between transverse electric mode andradiation is an integral multiple of 2π and the output radiation islinearly polarized; (3) a pair of elongated strip electrodes parallel tothe waveguiding direction and situated in an intermediate zone betweenthe positioned coupling means, and said electrodes are connected to avoltage source and are in a spaced proximity for application of auniform electric field to the thin film waveguide; wherein the device isadapted to modulate waveguided radiation by refractive index change inthe waveguide medium in accordance with the following equations:##EQU1## where Γ is the radiation phase retardation; Γ_(o) is theradiation phase retardation by the thin film waveguide medium; δφ is theradiation phase shift caused by the applied voltage; I is the inputelectromagnetic radiation signal; and I_(o) is the outputelectromagnetic radiation signal; and wherein the device is incombination with (4) a linearly polarized coherent electromagneticradiation generating means; and (5) a polarization-sensitive analyzer.

In a further embodiment this invention provides a thin film waveguideelectrooptic intensity modulation device comprising (1) a transparentoptical waveguiding thin film on a supporting substrate, wherein thethin film comprises an isotropic organic polymer medium which exhibitsnonlinear optical response, and the waveguiding thin film is laminatedbetween two cladding layers which have a lower index of refraction thanthe cladded thin film; (2) a pair of optical input-output coupling meanswhich are structurally integrated with the waveguiding thin film forcoupling linearly polarized coherent electromagnetic radiation to thesaid thin film, wherein the coupling means are in spaced positions suchthat an optical phase shift between transverse electric mode andtransverse magnetic mode of waveguided electromagnetic radiation is anintegral multiple of 2π and the output radiation is linearly polarized;(3) a pair of elongated strip electrodes parallel to the waveguidingdirection and situated in an intermediate zone between the positionedcoupling means, and said electrodes are connected to a voltage sourceand are in a spaced proximity for application of a uniform electricfield to the thin film waveguide; wherein the device is adapted tomodulate waveguided radiation by refractive index change in thewaveguide medium in accordance with the following equations: ##EQU2##where Γ is the radiation phase retardation; Γ_(o) is the radiation phaseretardation by the thin film waveguide medium; δφ is the radiation phaseshift caused by the applied voltage; I is the input electromagneticradiation signal; and I_(o) is the output electromagnetic radiationsignal; and wherein the device is in combination with (4) a linearlypolarized coherent electromagnetic radiation generating means; (5) apolarization-sensitive analyzer; and (6) a photodetector means.

The Kerr effect and Pockels effect in the Γ phase retardationrespectively correspond to the equations: ##EQU3## where l is the lengthof the electrode pair; λ is the optical wavelength; η₂ is the Kerrcoefficient; V is the applied voltage; d is the distance betweenelectrodes ; η is the index of refraction of the waveguide film; and ris the Pockels coefficient.

When Γ_(o) =π/2 and δφ<<Γ_(o), V=V_(m) sin ω_(m) t. The input-outputsignals are represented by the equations: ##EQU4## where Γ' is aconstant; ω_(m) is the angular frequency of the applied AC field; V_(m)is the amplitude of the voltage; and t is the time in seconds.

The applied voltage can be AC or DC, and typically will vary betweenabout 0-400 volts, and the frequency of the applied field will varybetween DC and gigahertz region.

Referring to the drawing, FIG. 1 is a perspective view of a thin filmwaveguide electrooptic intensity modulation device in accordance withthe present invention.

The waveguide electrooptic device 10 in FIG. 1 is a construction ofcomposite layers consisting of substrate 12; a pair of elongated stripelectrodes 14; a nonlinear optically active organic polymer thin film15; a first cladding layer 16 and a second cladding layer 17; and a pairof prism coupling means 20.

In practice Device 10 is utilized in combination with polarized laserradiation source 21 which provides input laser beam 22; polarizer 23which functions as a polarization-sensitive analyzer; and photodetector24 which functions to convert output signal 25 to a reconstructedelectrical signal. Waveguided radiation 26 is coupled to thin film 15with the pair of prism coupling means 20.

The term "transparent" as employed herein refers to a thin filmwaveguide medium which is transparent or light transmitting with respectto incident fundamental and created light frequencies. In a presentinvention waveguide electrooptic device, the thin film nonlinear opticalmedium is transparent to both the incident and exit light frequencies.

The term "isotropic" as employed herein refers to a transparent thinfilm organic waveguide medium in which the optical properties areequivalent in all tensor directions.

The term "external field" as employed herein refers to an electric,magnetic or mechanical stress field which is applied to a substrate ofmobile organic molecules, to induce dipolar alignment of the moleculesparallel to the field.

The input linearly polarized coherent electromagnetic radiationpreferably is a laser beam such as a helium-neon (0.6328 micron) laseror an argon-neon laser (0.5145 or 0.4880 micron).

The coupling means can consist of a pair of prism couplers, such asSchott SF₆ optical glass with a high index of refraction. Opticalcoupling and decoupling also can be accomplished with opticaldiffraction gratings which are formed directly on the surface of thethin film waveguide, as described in U.S. Pat. Nos. 3,674,335;3,874,782; and 3,990,775.

The substrate 12 as illustrated in FIG. 1 can he constructed of anyconvenient non-conducting medium such as plastic or glass.

The thin film organic waveguiding medium of the invention electroopticdevice is transparent and isotropic, and exhibits nonlinear opticalresponse.

A typical thin film organic medium comprises a blend of a polymer hostand a guest component. The nonlinear optical properties of the thin filmcan be controlled by the guest component alone, or both the host and theguest components can exhibit nonlinear optical susceptibility.

Illustrative of suitable host polymers are poly(methyl methacrylate),cellulose acetate, polysiloxane, polyacrylamide polyacrylonitrile, andthe like.

Illustrative of suitable guest compounds are 4-nitroaniline,2-methyl-4-nitroaniline, 4-N,N-dimethylamino-4'-nitrostilbene(DANS), andthe like.

Other suitable nonlinear optically active guest compounds areillustrated by quinodimethane structures corresponding to the formulae:##STR1## where n is an integer with a value between about 0-3; R and R¹are substituents selected from hydrogen and aliphatic, alicyclic andaromatic groups containing between about 1-20 carbon atoms, and at leastone of the R substituents is an electron-donating group, and at least ofthe R¹ substituents is an electron-withdrawing group.

Illustrative of nonlinear optically active quinodimethane species are7,7-di(n-hexyldecylamino)-8,8-dicyanoquinodimethane;13,13-diamino-14,14-dicyanodiphenoquinodimethane;13,13-di(dimethylamino)-14,14-dicyanodiphenoquinodimethane;13,13-di(n-hexadecylamino)-14,14-dicyanodiphenoquinodimethane;13,13-ethylenediamino-14,14-dicyanodiphenoquinodimethane;13,13-di(dimethylamino)-14,14-dicyano-4,5,9,10-tetrahydropyrenoquinodimethane;13,13-di(n-hexadecylamino)-14,14-dicyano-4,5,9,10-tetrahydropyrenoquinodimethane;and the like.

The synthesis of quinodimethane compounds as listed above is describedin copending patent application Ser. No. 748,583, filed June 25, 1985;and copending patent application Ser. No. 864,203, filed May 19, 1986;incorporated herein by reference.

The term "electron-donating" as employed herein refers to organicsubstituents which contribute electron density to the π-electron systemwhen the conjugated electronic structure is polarized by the input ofelectromagnetic energy.

The term "electron-withdrawing" as employed herein refers toelectronegative organic substituents which attract electron density fromthe π-electron system when the conjugated electron structure ispolarized by the input of electromagnetic energy.

A particular host polymer is selected for ease of fabrication, opticalproperties, and compatibility with the organic guest component. Theguest component typically will constitute between about 5-60 weightpercent of a thin film waveguide guest/host medium.

A polymer which exhibits nonlinear optical response can be employed as ahost component, or it can be utilized as a sole component. This type oforganic component is illustrated by thermoplastic polymers which arecharacterized by a recurring monomeric unit corresponding to theformula: ##STR2## where P is a polymer main chain unit, S is a flexiblespacer group having a linear chain length of between about 0-20 atoms, Mis a pendant group which exhibits a second order nonlinear opticalsusceptibility B of at least about 5×10⁻³⁰ esu as measured at 1.91 μmexcitation wavelength, and where the pendant groups comprise at leastabout 10 weight percent of the polymer, and the polymer has a glasstransition temperature above about 40° C..

Isotropic phase side chain liquid crystalline polymeric media exhibitingthird order nonlinear optical response are described in copending patentapplication Ser. No. 915,180, filed Oct. 3, 1986.

In another embodiment this invention contemplates a thin film waveguidemedium which has an external field-induced alignment of moleculardipoles, such as nonlinear optically active guest molecules, ornonlinear optically active mesogenic side chains of polymers asdescribed above.

Poling of a thin film waveguide medium can be accomplished convenientlyby heating the medium near or above its melting point or glasstransition temperature, then applying a DC electric field (e.g.,400-100,000 V/cm) to the medium to align molecular dipoles in a uniaxialorientation. The medium then is cooled while the medium is still underthe influence of the applied DC electric field. In this manner a stableand permanent molecular orientation is immobilized in a rigid structure.

A nonlinear optically active thin film waveguide medium can exhibit aKerr effect, and then after poling can exhibit a Pockels effect. Acentrosymmetric optical medium exhibits third order nonlinear opticalsusceptibility χ.sup.(3), linear optical susceptibility χ.sup.(2).

Theoretical considerations in connection with nonlinear optics areelaborated by Garito et al in chapter 1 of the ACS Symposium Series 233(1983); and by Lipscomb et al in J. Chem., Phys., 75, 1509 (1981),incorporated herein by reference. See also Lalama et al, Phys. Rev.,A20, 1179 (1979); and Garito et al, Mol. Cryst. and Liq. Cryst., 106,219 (1084); incorporated herein by reference.

A present invention thin film waveguide medium preferably is coated oneach surface with a cladding layer, and the cladding layers have a lowerindex of refraction than does the cladded thin film waveguide. The pairof cladding layers can be organic or inorganic, and can be the same ordifferent.

The thin film waveguide layer and the cladding layers, respectively, canbe composited with the substrate as shown in FIG. 1 by conventionalfabricating techniques such as spin coating, spraying, Langmuir-Blodgettdeposition, sputtering, and the like, as appropriate for the respectivematerials.

One preferred type of cladding layer is spin coated glass. Another typeis a cladding layer of an organic polymer such as polyvinyl alcohol,polyvinyl acetate, polyethylene oxide, poly(vinyl methyl ether), and thelike.

Electrodes 14 in FIG. 1 can be a strip coating of a suitable conductingmaterial such as aluminum, silver, gold, copper, indium-tin oxide,indium titanate, and the like, and are connected to a DC or AC powersource.

The output beam of linearly polarized radiation which emits from thecoupling means is directed through a polarization-analyzer means, thatin FIG. 1 is represented as a polarizer which is in a crossed moderelative to the polarization plane of waveguided radiation in theabsence of a moderating electric field.

When the FIG. 1 electrooptic system is operational, the electric fieldin the thin waveguide modulates waveguided radiation by change inrefractive index commensurate with change in the electric field. Theelectric field causes a phase shift between the transverse electric (TE)and transverse magnetic (TM) modes of the electromagnetic radiationwhich is coupled in the thin film waveguide.

As the voltage increases in the device, the degree of rotation of theplane of polarized radiation increases. When the voltage increases fromzero to the half wave voltage, the polarization plane rotates aboutninety degrees. The amount of radiation which passes through the crossedpolarizer-analyzer as output signal increases from zero to fulltransmission of waveguided radiation, as the polarization plane rotatesover an arc of 90 degrees.

The following example is further illustrative of the present invention.The device components are presented as being typical, and variousmodifications in design and operation can be derived in view of theforegoing disclosure within the scope of the invention.

EXAMPLE

This Example illustrates the construction and operation of a waveguideelectrooptic device in accordance with the present invention.

FIG. 1 illustrates a present invention polymeric thin film electroopticmodulator which utilizes a phase shift between the electromagnetic TEand TM modes being transmitted by the thin film waveguide.

The device consists of a glass substrate with a coated InTiO₃ thin filmas the first electrode, one cladding layer on top of the InTiO₃ film,one layer of nonlinear optically active polymer as the guiding medium ontop of the cladding layer, a second cladding layer on top of the guidingfilm, and finally one conducting layer on top of the second claddinglayer.

The first cladding layer is SiO₂ formed by spin coating a glass solution(Allied 305) onto the glass substrate at 500 rpm for 8 seconds and 3000rpm for 25 seconds, and baking the coated substrate at 400° C. for onehour. The thickness of the cladding layer is 1 micron after a doublecoating process.

The waveguiding layer is composed of polymethylmethacrylate (PMMA)blended with a 10% content of para-nitroaniline (PNA) as a nonlinearoptically active component. The waveguiding layer is formed bydissolving 20% of the blend in trichloropropane and spin coating thesolution onto the substrate at 2000 rpm for 20 seconds to provide alayer with a thickness of 4 microns.

The second cladding layer is composed of 75% hydrolyzed polyvinylalcohol, which has an index of refraction slightly lower than that ofthe waveguiding layer. The second cladding layer is formed by spincoating a 30% water solution of the polyvinyl alcohol at 1300 rpm for 30seconds to provide a 2 micron cladding layer. The second cladding layeris removed from the two prism positions by dissolution in water, so thatthe coupling prisms are in direct contact with the waveguiding filminput-output coupling of waveguided radiation.

A linearly polarized laser beam is coupled into the guiding film by thefirst coupling prism. The polarization plane of the laser beam is at 45°relative to the incident plane so that both TE and TM modes are excitedwith equal intensities in the waveguide film. The beam is coupled out ofthe waveguide at the second coupling prism.

A polarizer is situated on the emerging beam with a polarization planeat 90° relative to the input beam polarization plane.

The output beam intensity is given by: ##EQU5## where I is the inputbeam intensity, and Γ is the phase retardation between the TE and TMmodes in accordance with the following equation: ##EQU6## where Γ_(o) isthe intrinsic phase retardation, δφ is the phase shift due to theapplied voltage V, which induces a change of the index of refraction inthe TM mode due to Pockels effect: ##EQU7## or Kerr effect: ##EQU8##where η is the index of refraction of the waveguide, r is the Pockelscoefficient, l is the length of the electrodes, d is the distancebetween the electrodes, λ is the beam wavelength, and η₂ is the Kerrcoefficient.

The intrinsic phase retardation mainly originates from the difference inthe effective index of refraction between the TE and TM modes. Byadjusting the second coupling prism to a position so that Γ_(o) is amultiple of 2π, the output intensity (eq. 1) vanishes, which correspondsto a linearly polarized emerging beam.

At an applied voltage (half wave voltage) where the phase shift δφ is π,the output beam intensity is maximized (eq. 1) which corresponds to a90° rotation of the input beam polarization. The device functions as ahigh contrast digital optical switch.

Linear modulation of the optical signal is obtained by inserting aquarter wave plate in between the output coupling prism and thepolarizer. With Γ_(o) =2mπ+π/2, δφ<<Γ_(o), and V=V_(m) sin ω_(m) t, forPockels effect eq. 1 is restated: ##EQU9##

Without external field poling of the nonlinear optically activemolecules, the waveguide medium is centrosymmetric and no Pockels effectis observed. The Kerr effect, which is contributed mainly from therotation of the PNA molecules in the polymer matrix, is the onlymechanism for radiation modulation. The response time of the rotation ofthe molecules governs the modulation.

The half wave voltage varies from 50 volts to 500 volts when the appliedvoltage frequency is changed from DC to 10 kHertz. Beyond 10 kHertz, thehalf wave voltage significantly increases.

Two methods are utilized to create the Pockels effect in the waveguidemedium of the device.

In the DC bias method, a DC voltage is applied to the electrodes of thedevice in addition to the AC voltage. The DC voltage aligns the PNAmolecules, which have a high permanent electric dipole moment, andinduces a noncentrosymmetry within the waveguide medium. The Pockelseffect arises from the intrinsic second order optical response of thePNA molecules. The Pockels coefficient depends on the DC voltage. Thedevice serves as a controllable optical switch and a gain controllablelinear optical modulator by varying the applied DC voltage.

In the poling method, the device is heated to just below the phasetransition temperature of the polymer, and a high voltage is applied tothe electrodes. The PNA molecules are aligned by the high voltage. Thedevice is cooled slowly while maintaining the applied field. The voltageis removed after the device has cooled to room temperature. The PNAmolecular orientation provides a noncentrosymmetric medium, and aPockels effect is observed. The half wave voltage of the device from thePockels effect is around 700 volts.

What is claimed is:
 1. A thin film waveguide electrooptic intensitymodulation device comprising (1) a transparent optical waveguiding thinfilm on a supporting substrate, wherein the thin film comprises anorganic polymer medium which exhibits nonlinear optical response, andthe waveguiding thin film is laminated between two cladding layers whichhave a lower index of refraction than the cladded thin film; (2) a pairof optical input-output coupling means which are structurally integratedwith the waveguiding thin film for coupling linearly polarized coherentelectromagnetic radiation to the said thin film, wherein the couplingmeans are in spaced positions such that there is an optical phase shiftbetween transverse electric mode and transverse magnetic mode ofwaveguided electromagnetic radiation which is an integral multiple of πand the output radiation is linearly polarized; and (3) a pair ofelongated strip electrodes parallel to the waveguiding direction andsituated in an intermediate zone between the positioned coupling means,and said electrodes are connected to a voltage source and are in aspaced proximity for application of a uniform electric field to the thinfilm waveguide; and wherein the device is adapted to modulate waveguidedradiation by refractive index change in the waveguide medium inaccordance with the following equations: ##EQU10## where Γ is theradiation phase retardation; Γ_(o) is the radiation phase retardation bythe thin film waveguide medium; δφ is the radiation phase shift causedby the applied voltage; I is the input electromagnetic radiation signal;and I_(o) is the output electromagnetic radiation signal.
 2. A thin filmwaveguide electrooptic intensity modulation device comprising(1) atransparent optical waveguiding thin film a supporting substrate,wherein the thin film comprises an organic polymer medium which exhibitsnonlinear optical response, and the waveguiding thin film is laminatedbetween two cladding layers which have a lower index of refraction thanthe cladded thin film; (2) a pair of optical input-output coupling meanswhich are structurally integrated with the waveguiding thin film forcoupling linearly polarized coherent electromagnetic radiation to thesaid thin film, wherein the coupling means are in spaced positions suchthat an optical phase shift between transverse electric mode andtransverse magnetic mode of waveguided electromagnetic radiation is anintegral multiple of 2π the output radiation is linearly polarized; (3)a pair of elongated strip electrodes parallel to the waveguidingdirection and situated in an intermediate zone between the positionedcoupling means, and said electrodes are connected to a voltage sourceand are in a spaced proximity for application of a uniform electricfield to the thin film waveguide; and wherein the device is adapted tomodulate waveguided radiation by refractive index change in thewaveguide medium in accordance with the following equations: ##EQU11##where Γ is the radiation phase retardation; Γ_(o) is the radiation phaseretardation by the thin film waveguide medium; δφ is the radiation phaseshift caused by the applied voltage; I is the input electromagneticradiation signal; I_(o) is the output electromagnetic radiation signal;and wherein the device is in combination with (4) a linearly polarizedcoherent electromagnetic radiation generating means; and (5) apolarization-sensitive analyzer.
 3. A thin film waveguide electroopticintensity modulation device comprising (1) a transparent opticalwaveguiding thin film on a supporting substrate, wherein the thin filmcomprises an organic medium which exhibits nonlinear optical response;(2) a pair of optical input-output coupling means which are structurallyintegrated with the waveguiding thin film for coupling linearlypolarized coherent electromagnetic radiation to the said thin film,wherein the coupling means are in spaced positions such that there is aphase shift between transverse electric mode and transverse magneticmode of waveguided electromagnetic radiation and the output radiation ispolarized with a phase relationship between orthogonal components asdetermined by the coupling means spacing; and (3) a pair of elongatestrip electrodes parallel to the waveguiding direction and situated inan intermediate zone between the positioned coupling means, and saidelectrodes are in a spaced proximity for application of a uniformelectric field to the thin film waveguide.